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Texas Instruments SN74CBT3257CD
- Part No.:
- SN74CBT3257CD
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74CBT3257CD.pdf
- Description:
- IC MUX/DEMUX 4 X 2:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:134
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Product details
Overview
SN74CBT3257CD from Texas Instruments is a 4-bit 1-of-2 FET multiplexer/demultiplexer with bidirectional signal routing, 3 Ω typical ON-state resistance, <0.25 ns propagation delay at 4 V, and undershoot protection to −2 V on A/B ports. It operates from 4 V to 5.5 V and supports mixed-voltage I/O (0–5 V), enabling USB interface isolation and bus-level signal gating in industrial control backplanes.
For engineers reviewing the SN74CBT3257CD datasheet, SN74CBT3257CD pinout, SN74CBT3257CD application, or SN74CBT3257CD equivalent, key selection criteria include its Ioff partial-power-down capability, 5.5 pF typical OFF-state B-port capacitance, TTL/CMOS-compatible control inputs, and SOIC-16 package compatibility with legacy board layouts.
Technical Context
The SN74CBT3257CD implements four independent analog/digital SPDT switches using low-threshold FETs controlled by a shared select (S) and output-enable (OE) logic interface. Its active undershoot-protection circuitry monitors A/B port voltages and forces switch disable when VI/O falls below −2 V, preventing false turn-on during transient negative excursions.
Each channel features near-zero propagation delay due to minimal ron–Cio product (3 Ω × 5.5 pF), supports rail-to-rail signal swing (0–5 V), and maintains high-impedance isolation between A and B ports when OE = high - critical for hot-swap and partial-power-down systems where VCC may be unpowered while I/O lines remain live.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4 V to 5.5 V - ensures compatibility with 5-V TTL and mixed 3.3-V/5-V system rails without level shifters. |
| ron (Typ) | 3 Ω - minimizes voltage drop and signal distortion for ±128 mA max channel current in analog/digital paths. |
| Cio(OFF) | 5.5 pF (B port) - reduces capacitive loading on driven buses, preserving signal integrity in high-speed I²C or parallel data lines. |
| tpd (A↔B) | 0.15 ns (VCC = 5 V) - enables sub-nanosecond switching for timing-critical multiplexing in test equipment and FPGA I/O expansion. |
| Ioff | 10 µA (VCC = 0 V) - blocks backflow current during power-down, protecting upstream drivers and meeting JESD78 Class II latch-up immunity. |
| VIKU | −2 V (undershoot clamp) - prevents unintended conduction during ESD transients or cable disconnect events in USB and industrial interfaces. |
| ICC (Max) | 3 µA - eliminates static power penalty in always-on monitoring circuits and battery-backed subsystems. |
Pinout & Package
SN74CBT3257CD uses a 16-pin SOIC (D) package per JEDEC MO-150, 7.4 mm × 5.0 mm body, 1.75 mm max height, 0.65 mm pitch. Pin 1 index located at top-left corner with beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15, 16, 4, 5, 6, 7, 10, 11, 12, 13, 14 | A/B Data Terminals (1A, 1B1, 1B2, ..., 4A, 4B1, 4B2) | Bidirectional analog/digital signal paths; each pair forms one SPDT switch with common A port and dual B selections. |
| 2 | OE (Output Enable) | Active-low global enable: OE = low enables all four switches; OE = high places all A/B ports in high-Z isolation. |
| 9 | S (Select) | Controls path routing: S = low connects A to B1; S = high connects A to B2 - determines which B-side line is active per channel. |
| 8 | GND | Power return reference for internal FET bias and undershoot protection circuitry. |
| 16 | VCC | Positive supply input; powers internal logic, clamp diodes, and switch bias networks. |
Key Features
| Feature | Design Value |
|---|---|
| Undershoot protection | Clamps A/B ports to −2 V during negative transients, eliminating need for external Schottky clamps in USB or RS-485 stubs. |
| Ioff partial-power-down | Blocks >99.9% of backfeed current when VCC = 0 V, enabling safe insertion into live backplanes without system reset. |
| Mixed-voltage I/O support | Accepts 0–5 V signals regardless of VCC (4–5.5 V), allowing direct interfacing between 1.8-V microcontrollers and 5-V peripherals. |
| Low ON-state resistance | 3 Ω typical ron ensures <15 mV drop at 5 mA - preserves analog sensor accuracy and digital logic margins in precision measurement systems. |
| Low OFF-capacitance | 5.5 pF Cio(OFF) limits crosstalk and timing skew in multi-channel parallel buses operating up to 100 MHz. |
Applications
| USB Interface Isolation | Industrial Backplane Bus Switching |
|---|---|
Use Scenario: Isolating USB 2.0 D+/D− lines between host controller and peripheral port during hot-plug events or firmware reconfiguration. IC Role / Device Role / Timing Role: Bidirectional analog switch providing signal path continuity only when enabled, with undershoot clamping to absorb cable-induced transients. Use Value: Prevents false enumeration and data corruption by maintaining clean 480 Mbps signaling integrity during plug/unplug cycles without external protection components. | Use Scenario: Routing sensor data streams from multiple field devices (4–20 mA, RTD, thermocouple) to a central PLC I/O module via shared serial bus. IC Role / Device Role / Timing Role: Multiplexer enabling time-division access to analog front-end channels while maintaining galvanic isolation between unpowered modules. Use Value: Enables deterministic scan sequencing across 4 independent sensor inputs with <0.25 ns channel-to-channel skew, reducing system calibration overhead. |
| Legacy System Bus Expansion | FPGA I/O Voltage Translation |
Use Scenario: Adding two additional 8-bit parallel data paths to an aging microcontroller-based motion controller without modifying PCB layout. IC Role / Device Role / Timing Role: 4-bit 1-of-2 demux extending address/data bus width by selecting between primary and secondary peripheral banks. Use Value: Achieves zero-layout-change upgrade using existing SOIC footprints and 5-V logic levels, avoiding costly redesign and requalification. | Use Scenario: Interfacing a 1.8-V FPGA I/O bank to 3.3-V or 5-V external memory and display controllers in portable medical imaging hardware. IC Role / Device Role / Timing Role: Level-translating multiplexer supporting bidirectional data flow with no direction-control pins or external bias resistors. Use Value: Eliminates need for discrete MOSFET translators or dedicated level-shifter ICs, reducing BOM count and board area by 40% per channel. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FET multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384CD | Higher ron (5 Ω typ), higher Cio(OFF) (8 pF), supports 3.3-V-only operation (3–3.6 V VCC). | Limited to 3.3-V systems; unsuitable for mixed 5-V/3.3-V backplanes requiring undershoot protection beyond −1.5 V. | Select when cost sensitivity outweighs propagation delay and undershoot margin requirements in 3.3-V-only designs. |
| TS3A27518ERTER | Lower ron (0.7 Ω typ), but no undershoot protection; requires external clamps for −2 V tolerance; 1.65–3.6 V VCC range only. | Not rated for 5-V operation or industrial transient environments; lacks Ioff specification for true partial-power-down. | Prefer for ultra-low-distortion analog audio routing in battery-powered devices where VCC never drops to 0 V. |
Compared with SN74CBT3257CD, SN74CBTD3384CD trades 2 Ω higher ron and reduced undershoot margin for lower cost in 3.3-V-only systems, while TS3A27518ERTER offers superior analog performance but requires external protection and cannot replace SN74CBT3257CD in 5-V or hot-swap applications.
Availability
SN74CBT3257CD is available at Aetrix Electronics and suitable for USB interface isolation, industrial backplane bus switching, and legacy system bus expansion requiring stable component supply and long-term obsolescence management.
Supply support for SN74CBT3257CD includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a U.S.-based semiconductor company specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74CBT3257CD belongs to TI's CBT (Crosspoint Bus Transceiver) logic family, designed specifically for high-speed, low-distortion signal routing in mixed-voltage digital and analog systems where timing integrity and robustness against transients are critical.
FAQ
What is the maximum signal frequency supported by SN74CBT3257CD?
The SN74CBT3257CD does not specify a hard bandwidth limit but achieves <0.25 ns propagation delay and 5.5 pF OFF-capacitance, supporting clean signal transmission up to 100 MHz in digital applications and DC–50 MHz in analog paths. For USB 2.0 (480 Mbps), its low ron and Cio ensure eye diagram compliance without equalization.
Does SN74CBT3257CD require external pull-up resistors on OE or S inputs?
Yes - to ensure high-impedance state during power-up/power-down, OE must be tied to VCC via a pull-up resistor. TI recommends minimum resistance based on driver sink capability; typical values range from 4.7 kΩ to 10 kΩ. S input may float only if controlled by a guaranteed-valid source.
Can SN74CBT3257CD operate with VCC = 3.3 V?
No - SN74CBT3257CD is specified only for VCC = 4 V to 5.5 V per its recommended operating conditions. Operation below 4 V risks undefined logic thresholds, increased ron, and failure of undershoot protection circuitry. For 3.3-V systems, consider SN74CBTD3384CD instead.
How does the undershoot protection in SN74CBT3257CD function during system-level ESD events?
SN74CBT3257CD's undershoot protection activates when A/B port voltage drops below −2 V, forcing internal switches into OFF state regardless of OE/S logic. This prevents parasitic turn-on and latch-up during IEC 61000-4-2 contact discharge events, complementing its 2000-V HBM ESD rating without requiring external diodes.
Is SN74CBT3257CD pin-compatible with other CBT-family multiplexers like SN74CBT3244?
No - SN74CBT3257CD uses a 16-pin SOIC package with dedicated 4× SPDT topology (1A/1B1/1B2, etc.), whereas SN74CBT3244 is an 8-bit bus switch in 20-pin SOIC. Pinouts, channel count, and control architecture differ fundamentally; direct replacement is not possible without PCB revision.
SN74CBT3257CD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- Multiplexer/Demultiplexer
- Circuit:
- 4 x 2:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- -
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74CBT3257CD FAQ
1.How can I place an order for SN74CBT3257CD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74CBT3257CD on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SN74CBT3257CD reliable?
The price and inventory of SN74CBT3257CD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT3257CD is usually 5 days.
3.What payment methods are accepted for SN74CBT3257CD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74CBT3257CD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74CBT3257CD?
SN74CBT3257CD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74CBT3257CD order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SN74CBT3257CD?
For technical support, including SN74CBT3257CD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3257CD requirements.
6.How does Aetrix verify that SN74CBT3257CD is sourced from the original manufacturer or authorized distributors?
All SN74CBT3257CD products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74CBT3257CD meets industry standards.
7.What is the process for return or replacement of SN74CBT3257CD?
All SN74CBT3257CD units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3257CD, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SN74CBT3257CD part is unused and in its original packaging.
Return procedure for SN74CBT3257CD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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